In my opinion, for your consideration, Ni-Rod or Certanium is the best for cast. That stuff is around $30-50 a pound. Aside from that, I'd just preheat it and use a Mig. Migs work pretty good on any good casting. (Gas-shielded) Preheat to 500 degrees (check it with a digital thermometer) weld it up, then wrap it in a welding blanket or bury it in sand to let it cool as slow as possible. Grind it out after or mill it if you have the option. You're only doing cosmetic work so you should have no issues with cracks.
My buddy ran a 2" hole-saw almost through the table on my Chinese drill press. He's an Industrial Electrician and everyone knows that they need supervision; my fault. (Good thing that I didn't let him use the mill). Anyway, I welded it up, cold, with the mig, ground it down, blended it in; no cooling, no issues. And that's on a thin, cheap casting.
Oxy Acetylene Brazing would be my second choice but gas welding procedures introduce a lot of heat into the weldment. A vise should be able to take it but still let her cool as slow as possible.
J.B. - type products; I have less confidence/experience with. I worry about the possibility of oil infiltration causing an eventual bond-failure. Then again it is, largely, only cosmetic and that would be the simplest solution.
Bottom line, regardless of what procedure you choose; get it clean, clean. Acetone or Tolulene, Methyl Hydrate, etc.